Optical recording medium, method for recording/reproducing the optical

ABSTRACT

An optical recording medium for accurately deriving the address information or the disc rotation control information despite narrow track pitch and for recording signals to a high density, and a method and apparatus for recording and/or reproducing such optical recording medium. The optical recording medium has a wobbled groove and pits formed at a pre-set interval in an area between turns of the wobbled groove. The recording/reproducing method includes controlling rotation of the optical recording medium by a wobbled signal from the groove and detecting the position on the optical recording medium of a recording signal by pit signals detected from the pits. The recording/reproducing apparatus includes a detection device for detecting the wobbled signal from the groove and a detection device for detecting pit signals from the pits. The rotation of the optical recording medium is controlled by the wobbled signals detected from the groove and the position on the optical recording medium of the recording signal is detected by the pit signal detected from the pits.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to an optical recording medium having awobbled groove, more particularly, to a novel optical recording mediumcapable of recording signals to a high density. The invention alsorelates to a method and apparatus for recording and/or reproducing suchoptical recording medium.

[0003] 2. Description of the Related Art

[0004] The CD-R disc, used in, for example, a so-called compact discrecordable system (CD-R), has a wobbled groove. The sector information,inclusive of the address information, is recorded by modulating thewobbled signal.

[0005] Specifically, in a CD-R recording and/or reproducing apparatus,the wobbled signal having 22 kHz as carrier wave, is detected by arecording and/or reproducing light spot converged on the groove. A datastring including the address information is detected by FM demodulatingthe wobbled signal.

[0006] In a system in which the address is arrayed at the leading end ofthe sector, the address information and the recording information arerecorded time-divisionally, so that the recorded signals becomediscontinuous signals. With the present system, the data can be recordedcontinuously. Such feature is meritorious for an application in whichemphasis is placed on interchangeability with the read-only disc onwhich the signals are recorded continuously.

[0007] In a method of recording the address information by modulatingthe wobbled signal, if the track pitch, which is the distance betweenneighboring groves, is reduced, the leakage of the wobbled signal fromthe neighboring groove is increased, thus lowering the S/N ratio of thewobbled signal. The address information not only cannot be demodulatedcorrectly, but also the carrier wave of the wobbled signal, required forrotational control of the disc, becomes difficult to detect thus givingrise to obstructions in rotational control of the disc.

[0008] Since it s necessary to reduce the track pitch for recording thesignal to a high density, it becomes necessary to reproduce the addressinformation correctly despite the narrow track pitch.

[0009] Also, in the above system, the recording and/or reproducing spoton the disc derived from the reproduced address information depends asto its position accuracy on the frequency of the carrier wave and issubstantially on the order of the wavelength of the carrier wave. On theother hand, the frequency of the carrier wave, that is the wobblingfrequency, needs to be selected to a lower value in order to avoidadverse effects on the recording signal. In the case of the CD-R, thewobbling frequency is 22 kHz, with the wavelength on the disc being 54μm.

[0010] If data is recorded discontinuously, that is with interruptions,and data is recorded subsequently in the non-recorded portion, it isnecessary to record data in correct positions on the disc. If correctrecording is not possible, a so-called gap needs to be provided forabsorbing errors in recording positions from one recording data unit toanother for avoiding overlapping between recording data.

[0011] Since the gap reduces the recording capacity on the disc, the gaplength needs be reduced to as small a value as possible. However, theabove-mentioned accuracy is not sufficient.

SUMMARY OF THE INVENTION

[0012] It is therefore an object of the present invention to provide anoptical recording medium in which the address information and the discrotation control information can be correctly obtained despite thenarrow track pitch to enable the signal to be recorded to high density.

[0013] It is another object of the present invention to provide a methodand apparatus for recording/reproducing the optical disc.

[0014] In one aspect, the present invention provides an opticalrecording medium having a wobbled groove and pits formed at a pre-setinterval in an area between turns of the wobbled groove.

[0015] In another aspect, the present invention provides a method forrecording and/or reproducing signals to an optical recording mediumhaving a wobbled groove and pits formed at a pre-set interval in an areabetween turns of the wobbled groove. The recording method includescontrolling rotation of the optical recording medium by a wobbled signalfrom the groove and detecting the position on the optical recordingmedium of a recording signal by pit signals detected from the pits.

[0016] In another aspect, the present invention provides a recordingand/or reproducing apparatus including an optical recording mediumhaving a wobbled groove and pits formed at a pre-set interval in an areabetween turns of the wobbled groove, detection means for detecting awobbled signal from said groove and detection means for detecting pitsignals from the pits, wherein rotation of the optical recording mediumis controlled by the wobbled signals detected from the groove andwherein the position on the optical recording medium of the recordingsignal is detected by the pit signal detected from the pits.

[0017] With the above configuration of the present invention, theaddress information and the rotation control information for the opticalrecording medium can be obtained accurately despite narrow track pitchthus contributing to high density recording.

[0018] The response speed and reliability of rotational control of theoptical recording medium may also be improved simultaneously. Forexample, if rotation of the CLV disc is controlled by only landpre-pits, these pre-pits cannot temporarily cannot be detected if thelinear velocity is changed significantly due to random accessing, suchthat considerable time is consumed until the pre-pits are again detectedto resume the rotational control. This inconvenience is resolved byusing the wobbled pits and the pit signals simultaneously.

[0019] In addition, it is possible with the present invention to derivethe address information more accurately and with high time precisionthan is possible with the conventional technique.

[0020] Moreover, if, with the optical recording medium of the presentinvention, the wobbled signal and the address signals are read by thesole beam spot, it becomes possible to detect the playback signalcorresponding to the recording signal, servo signals (focusing servo andtracking servo signal), wobbled signal and the address information intheir entirety, thus simplifying the recording/reproducing apparatus andenabling the recording/reproducing apparatus to be manufactured atreduced cost.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a schematic view showing an example in which a pit isformed at the center of wobbling.

[0022]FIG. 2 is a schematic view showing an example in which thewobbling amount is maximum and a pit has been formed at a positionproximate to a neighboring groove.

[0023]FIG. 3 is a schematic plan view showing essential portions of anexample of a groove and a pit in an optical recording medium embodyingthe present invention.

[0024]FIG. 4 is a waveform diagram showing a pulse signal obtained froma pit.

[0025]FIG. 5 shows a typical modulation of a synchronization pattern anda data pit.

[0026]FIG. 6 shows an example of a recording format for the addressinformation.

[0027]FIG. 7 is a circuit diagram showing an example of a signalreproducing circuit.

[0028]FIG. 8 is a waveform diagram showing an example of a playbacksignal in case the frequency of the wobbled signal and that of a pitsignal are in a integer ration relationship to each other.

[0029]FIG. 9 is a waveform diagram showing an example of a playbacksignal in case the wobbled signal and pit signal are in phase with eachother.

[0030]FIG. 10 is a waveform diagram showing an example of a playbacksignal in which synchronization signals are recorded in both the wobbledsignal and the pit signal.

[0031]FIG. 11 is a timing chart in case the wobbled signal and the pitsignal are in phase with each other.

[0032]FIG. 12 is a block diagram showing an example of a playbackcircuit in a reproducing apparatus.

[0033]FIG. 13 is a timing chart in case synchronization signals arerecorded in both the wobbled signal and the pit signal.

[0034]FIG. 14 is a timing chart in which a pre-pit string leading endjudgment signal is inserted as a wobbled signal.

[0035]FIG. 15 is a schematic plan view showing a modification of thegroove and the pit.

DESCRIPTION OF THE INVENTION

[0036] An optical recording medium according to the present inventionhas a wobbled pre-groove and pits are formed at pre-set intervals in anarea defined between these grooves. The wobbled signal for the grooveand the pt signal for the pits are used in combination for enablinghigh-density recording.

[0037] The pits are formed in an area defined between neighboringgrooves, that is in a land. The pits may be in the form of usual pits ormay be formed continuously between neighboring grooves as cut-outs inthe lands interconnecting the neighboring lands.

[0038] These pits include the sector information inclusive of the syncpits or address pits, and the address information is obtained by thesector information. However, in the present invention, such sectorinformation is not always necessary such that it may be only necessaryto provide only sync pits or address pits. The sync pits indicate thestart position for the sector information and are formed as two pitsarranged in proximity to each other or as pits having pit lengthsdifferent from those of the other pits and hence can be detected asbeing distinct from the remaining pits.

[0039] On the other hand, a groove may have the wobbled signal of a solefrequency or may have the sector information in which the address datahas been recorded by modulation.

[0040] The sector information is the information associated with thesector of the recording data or a cluster which is a set of recordingdata sectors, and includes the synchronization signal and/or the addressdata.

[0041] The above groove or pit may be used in optional combination, suchthat, for example, the combination of the groove having the wobbledsignal of a sole frequency and sync pit or address pit, the combinationof the groove having the wobbled signal which is modulated for recordingthe sector information, such as synchronization signal or address data,and the sync pit or address pit, or the combination of the groove havingthe wobbled signal which is modulated for recording the sectorinformation and pits of a pre-set interval, may be employed.

[0042] If, in these combinations, the combination of the groove havingthe wobbled signal of a sole frequency and sync pit or address pit isemployed, the synchronization information and the address informationcan be reliably produced by these sync pits and address pits, while thedisc rotation control information can be positively produced by thewobbled signal.

[0043] If the wobbled signal is the signal of a sole frequency, anyleakage signal from a neighboring groove is precisely of the samefrequency as the frequency of the signal for detection, so that theeffect of leakage takes the from of slow changes in amplitude in thewobbled signal for detection, and hence the sole frequency for detectioncannot be detected easily.

[0044] If the combination of the groove having the wobbled signal whichis modulated for recording the sector information, such assynchronization signal or address data, and the sync pit or address pit,is used, the synchronization information or the address information isrecorded in duplicate in the groove and the pit, thus assuring increasedaccuracy is reliability.

[0045] If, when the groove and the pit are used in combination, the pitposition is formed at random relative to the groove, there is a fearthat the resulting playback signal is fluctuated in signal leveldepending on the pit position to render it difficult to detect the pitcorrectly. There is also a fear that the circuit for generating clocksin the reproducing apparatus becomes complex in structure.

[0046] For overcoming this drawback, it is desirable that the relationbetween the wobbled frequency fw (mean frequency) and the pit frequencyfp be an integer number relation as defined by the following equation:

M fw=N fp

[0047] where M and N are integers.

[0048] Stated differently, the wobbling period Tw and the pit period Tpare related to each other by an integer number relationship to eachother:

M Tw=N Tp

[0049] where M and N are integers.

[0050] Meanwhile, the wobble period Tw is an average wobbling period andthe pit period Tp is an interval which, if the pits are formed at aninterval equal to a pre-set integer number multiple of the pre-setinterval, is equal to such preset integer number multiple interval. Onthe other hand, in case two consecutive pits are sync pits, these twopits are deemed as a sole pit and the period between these two pits isdisregarded in setting the pit period Tp.

[0051] If the wobbling frequency fw and the pit frequency fp are relatedeach other by an integer number relationship as described above, itbecomes possible to unify reference clocks into one or use a solevoltage controlled oscillator, thus simplifying the clock generatingcircuit of the recording and/or reproducing apparatus.

[0052] In addition, it becomes possible to generate a signalsynchronized with the pit period from the wobbled signal by exploitingthe PLL, thereby enabling the pits to be detected correctly.

[0053] Alternatively, the wobbling phase and the pit phase may bematched to each other for enabling correct pit detection.

[0054] That is, by associating the pit position with a pre-set phase ofwobbling and by forming pits at a constant wobbling amount (meanderingamount of the groove), the pit detection signal may be stabilized forenabling the pits to be detected correctly.

[0055] In this case, a pit P may be formed at a wobbling center positionof a groove G (a position corresponding to the smallest wobblingamount), as shown in FIG. 1. Alternatively, the pit P may be formed at aposition proximate to the neighboring groove and corresponding to themaximum wobbling amount, as shown in FIG. 2. In the former case,cross-talk from other grooves becomes minimum, whereas, in the lattercase, the pit can be detected only by the signal level without removingwobbling signal component.

[0056] If the sector information inclusive of the synchronizationinformation or the address information is recorded in the wobbledsignal, and the pits include the sector information, such as the syncpits or address pits, it is desirable that the synchronizationinformation of the wobbling signals and the sector information,especially the sync pits, be at a pre-set positional relation to eachother. For example, the synchronization signal by wobbling is recordedwithin one pit period ahead of the sync pit in the reproducingdirection.

[0057] By previously comprehending the position of the synchronizationportion of the pit address from the wobbled signal, the pit addresssynchronization can be detected more correctly, as a result of which thepit address can be read out more reliably.

[0058] For recording/reproducing the above-described optical recordingmedium, disc rotation is controlled using a signal detected from awobbled groove, and the position of the recorded signal is controlled bythe information detected from the pits formed in the land.

[0059] The recording/reproducing apparatus can be simplified instructure by reading out the wobbled signal and the pit signalsimultaneously by the same beam spot using the push-pull method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] Referring to the drawings, preferred embodiments of the presentinvention will be explained in detail.

[0061] First Embodiment

[0062] An optical disc of the present embodiment is a write-once typedisc, 12 cm in diameter, having a recording film of an organic dye onwhich recording can be done using a laser beam having a wavelength of635 nm.

[0063] The disc is formed of polycarbonate and is produced by injectionmolding with a guide groove and a land between neighboring turns of theguide groove.

[0064] The groove is approximately 0.25 μm in width and approximately 70nm in depth and is formed as a continuous spiral groove from the innerrim to the outer rim, with the groove interval or track pitch ofapproximately 0.74 μm.

[0065] The wobbled signal of a sole frequency is recorded as theinformation for controlling the rpm of the disc and the clock frequencyof the recording signal. The wobbling means slight meandering of thegroove in the radial direction of the disc.

[0066] In the present embodiment, the meandering width is 20 nm and themeandering period is approximately 30 μm. Therefore, if the disc isrotated at a linear velocity of 3.5 m/sec for reproducing the wobbledsignal, the frequency is approximately 120 kHz.

[0067] In a land between neighboring turns of the groove, there isformed, as a pit for recording the address information (address pit), agroove approximately 0.3 μm in width and approximately 70 nm in depth,as is the guide groove.

[0068] Referring to FIG. 3, schematically showing the guide groove andthe address pit, address pits 2 are formed at a pre-set interval in anarea between neighboring turns of the wobbled guide groove 1. Theaddress pits 2 are formed continuously between neighboring turns of thegroove and are formed as grooves extending along the radius of the disc.

[0069] The address pits are formed at an interval of approximately 0.2mm in association with 1/0 of the information. That is, there is anaddress pit at a position corresponding to the information 1, whilethere is no address pit at a position corresponding to the information0. Therefore, the presence or absence of the address pit corresponds tothe 1/0 of the information.

[0070]FIG. 4 shows a signal obtained an scanning a beam spot B along thegroove. Specifically, there are obtained pulses of one polarity by theinner rim side address pits and those by the outer rim side address pitsof the opposite polarity. It suffices if the address information isdetected based on one of these two sorts of pulses.

[0071] In the present recording system, it may be presumed that, if æ0

of the information occur in succession, the state of absence of theaddress pits occurs in succession to render it difficult to detectaddress pits. In the present embodiment, the recording information ispreviously bi-phase modulated so that the number of contiguous æ0s

will be two at the maximum.

[0072] However, since the out-of-rule pattern of 000111 is provided inthe synchronization signal for facilitating detection of thesynchronization signal, thee is a portion in the synchronization signaldomain in which address pits are not recorded for three contiguouschannel bits.

[0073]FIG. 5 shows an example of modulation of data bits and thesynchronization pattern. The synchronization pattern is 0110001110001110thus containing three contiguous channel bits of 0 and 1 which are notprovided in the modulation rule.

[0074] The data bits are modulated so that 0 and 1 correspond to 1-0 and0-1, respectively, so that æ1s

or æ0s

contiguous for 3 or more channel bits are not contained in the dataportion.

[0075]FIG. 6 shows an example of the recording format for the sectorinformation. The sector information is made up of a sum total of 208channel bits, of which the leading 16 channel bits represent thesynchronization pattern. The address data of 8 bytes is followed by 4bytes of parity for error correction by the Reed-Solomon code.

[0076] In the present recording format, since up to 2 bytes can becorrected by the four bytes of parity, the address data can be correctlydetected if optional two channel bits of the 208 channel bits of thesector information are in error.

[0077] Next, signal reproduction of the above-described optical disc isexplained. Specifically, the method of simultaneously reading out thewobbled signal of the groove and the address signal of the pits by onebeam spot is explained.

[0078] Referring to FIG. 7, which is a block diagram of a signalreproducing circuit, the return light from a beam spot B converged onthe groove 1 is photo-electrically converted by four-segment PIN diodedetectors A, B, C and D and I-V converted to produce signals A, B, C andD corresponding to the respective diodes.

[0079] Of these signals, the sum of the signals (A+B+B+C) represents theplayback signal of the recorded signal. The sum signal is compensatedfor frequency response for recording/reproduction by an equalizercircuit 11 and converted to binary signals by a convert-to-binarycircuit 12 to produce playback signals, from which clocks for theplayback data are produced by a PLL circuit made up of a phasecomparator 13 and a voltage controlled oscillator (VCO) 14.

[0080] If the calculation of A−B+C−D is performed on the signals A, B, Cand D, focusing error signals of the astigmatic system are obtained.

[0081] The focusing error signal is sent via phase compensation circuit15 to a focusing driving circuit 16 from which a focusing driving signalcontrolling the focusing position of an objective lens is outputted.

[0082] If the calculation of A+B−C−D is performed on the signals A, B, Cand D, tracking error signals of the push-pull system are obtained.Since this signal is a signal corresponding to the relative position inthe radial direction of the groove and the beam spot B, the wobbledsignal of the groove is reproduced simultaneously. At a position inwhich an address pit is formed, a positive pulse or a negative pulse isdetected depending on whether an address bit is on the inner rim side oron the outer rim side with respect to the groove. These positive ornegative pulses are similarly included in the signal (A+B−C−D).

[0083] First, this signal (A+B−C−D) is passed through a low-pass filter(LPF) 17 to take out only the tracking error signal which is sent via aphase compensation circuit 18 to a tracking driving circuit 19 foroutputting the tracking driving signal.

[0084] For detecting pulse signals generated by the address pits, thereis employed a high-pass filter (HPF) 20 suppressing the signal less than130 kHz for avoiding the effect of the noise of the low frequency rangecaused by, for example, meandering by wobbling.

[0085] Since the wobbled signal is a narrow-band signal, a wobbledsignal of an optimum S/N ratio can be obtained by employing a band-passfilter (BPF) 21 capable of passing the narrow band. The resultingwobbled signal is converted to binary signals by a convert-to-binarycircuit 22. The resulting bi-level data is compared by a frequencycomparator circuit 23 to a reference frequency for producing a spindlemotor control signal.

[0086] As described above, it is possible with the present embodiment toproduce all signals required for signal reproduction using a solefour-segment PIN diode detector.

[0087] Second Embodiment

[0088] In the present embodiment, various combinations of the wobbledpits are explained.

[0089] In a first example, wobbling of a sole frequence and pits havinga integer number relation with respect to the frequency of the wobbledsignal is explained.

[0090] The signal obtained in this case is as shown in FIG. 8, fromwhich it is seen that pit signals Sp are detected at an interval equalto an integer times the period Tw of the wobbled signal Sw, that is atan interval equal to an integer times the pit period Tp.

[0091] In a second example, pits are formed in phase with the modulatedwobbled signal. In the present example, pits are formed at positionsproximate to the neighboring groove, corresponding to the maximumwobbling. The pit signals Sp are positioned at apices of the wobbledsignal Sw and pits are detected based only of the signal level of thepit signal Sp, as shown in FIG. 9.

[0092] In FIG. 9, the pit signal Sp is generated by the pit formed onthe inner rim side of the groove during tracking. On the other hand, thepit signal Sp

is generated by the pit formed on the outer rim side of the groove.

[0093] In the first example, pit signals are detected after removing thewobbled signals from the pit signals by a high-pass filter. In thepresent example, the wobbled signal is passed through the high-passfilter and pits are detected by comparing the pit signal Sp inclusive ofthe wobbled signal with the detection level L. The reason is that, ifthe frequency band of the wobbled signal is close to that of the pitsignals, it may be premeditated that difficulties are met in frequencyseparation by the high-pass filter.

[0094] In the present example, the pits on the inner rim side of thegroove are recorded at positions corresponding to the maximum wobblingof the groove towards the inner rim. In this case, the outer rim sidepit s formed at a maximum wobbling position towards the inner rim of anouter rim side neighboring groove.

[0095] The wobbled signal of a given turn of the groove and that of aneighboring turn are not necessarily coincident with each other.Therefore, if the pit signal Sp by the inner rim side pit is positionedat a position corresponding to the constant value of the wobbled signal,the pit signal Sp

by the outer rim side pit, recorded in association with another turn ofthe groove, is positioned in a manner irrelevant of the wobbled signal.

[0096] Referring to FIG. 9, the peak values of the pit signals Sp

by the outer rim side pit, formed at the positions irrelevant to thewobbled signal, are varied from pit to pit, while the peak values of thepit signals Sp by the inner rim side pits recorded at the constantwobbling positions, are constant.

[0097] If the peak values are constant, the peak values can be detectedeasily by a simple peak-hold circuit, despite variations in the pitsignal amplitudes, such that, by exploiting the detected peak values,the pit detection level can be kept at an optimum level to enable stablepit detection. This is a merit proper to the case in which pits areformed at substantially the constant wobbling amount.

[0098] Moreover, since the pit signals Sp are positioned at apices ofthe wobbled signal Sw, the tolerable variation width of the detectionlevel becomes maximum. This is a merit proper to the case in which pitpositions correspond to the maximum wobbling and are proximate to theneighboring groove.

[0099]FIG. 10 shows an example in which synchronization signals Sws arerecorded in the wobbled signal and combined with the sync pits Ssp.

[0100] In this case, the positions of the sync pits Ssp can bepreviously known from the synchronization signals Sws of the wobbledsignal for assuring more reliable detection of the sync pits Ssp. Thefollowing merits are derived from the above-described variouscombinations of the wobbling and the pits.

[0101] First, the case in which wobbling is in phase with the pits isexplained.

[0102]FIG. 11 shows a playback signal obtained from such optical disc.The playback signal is made up of the wobbled signal Sw and the pitsignals Sp corrupted by noise components Sn.

[0103]FIG. 12 shows, in a block diagram, a reproducing apparatus forreproducing the wobbled signal and the pit signals.

[0104] In the present reproducing apparatus, the wobbled signal Sw isfed via a band-pass filter 31 to a convert-to-binary circuit 32, whilethe pit signals Sp are fed via a by-pass filter 33 to aconvert-to-binary circuit 34, for conversion to respective binarysignals.

[0105] The convert-to-binary circuit 34 outputs the pit signals Sp andthe noise components Sn, as shown in FIG. 11B.

[0106] The wobbled signal Sw is further sent to a phase comparator 35for phase comparison to a signal obtained on 1/M*100 frequency divisionby a 1/100 frequency divider 37 and a 1/M frequency divider 38 of theoscillation frequency of the voltage controlled oscillator 36. Bycontrolling the voltage controlled oscillator 36 by the phaseinformation detected by the phase comparator 35, a phase-locked loop isformed, as a result of which a frequency Fo equal to (M*100) times thewobbled signal frequency Fw is outputted by the voltage controlledoscillator 36.

[0107] If the relation between the wobbling frequency Fw and the pitfrequency Fp is given by Fw*M=Fp*N, the oscillation frequency Fo of thevoltage controlled oscillator 36, given by Fo=Fw*(M*100)=Fp*(N*100), isequal to (N*100) times the pit frequency Fp.

[0108] Therefore, by frequency division of the output of the voltagecontrolled oscillator 36 by a 1/(N*100) counter 39, the phaseinformation shown in FIG. 11C is obtained, and outputted to a pit pulsedetection interpolation circuit 40.

[0109] By taking the AND of the phase information shown in FIG. 11C andthe output of the convert-to-binary circuit 34, the noise components Snare canceled, as shown in FIG. 11D, so that bit data clocks shown inFIG. 11E and the bit data as shown in FIG. 11F are outputted.

[0110] An example in which the synchronization (sync) signals arerecorded in the wobbled signal and combined with the sync pits is nowexplained.

[0111] Referring to FIG. 13, a wobbled signal shown at (a) isfrequency-modulated, and is demodulated to give a signal shown at (b).On the other hand, by arraying the sync of the pre-bit directly at backof the wobble sync, as shown at (c), the pre-bit sync can be detectedafter wobble sync detection.

[0112] The wobbling itself is not so accurate as the pre-pits. However,by providing an arrangement of pre-pit protection by a system differentfrom one by the pre-pits, it becomes possible to improve safety of thepre-pit signal itself.

[0113] As a method of use other than gating, a leading enddiscrimination signal of a pre-pit string can be inserted by wobbling,as shown in FIG. 14.

[0114] The result is that there is no necessity of forming the syncpattern by pre-pits thus raising the pre-pit accuracy. Since there is nonecessity of detecting the pre-pt sync pattern, circuit saving may berealized. In addition, the control circuit is duplicated, thus raisingthe reliability.

[0115] Although the foregoing description has been made of preferredembodiments of the present invention, it is to be noted that the presentinvention is not limited to these merely illustrative embodiments, butmay comprise various modifications or combinations.

[0116] For example, address pits 2 may be designed as ordinary pits.

[0117] If the sector information is recorded on both the wobbled signaland the pits, these may be used independently of each other. Forexample, it is possible to exploit the address information by the pitsbefore recording the signal and to exploit the address informationrecorded in the modulated state in the wobbled signal after recordingthe signal.

What is claimed is:
 1. An optical recording medium having a wobbled groove and pits formed at a pre-set interval in an area between turns of the wobbled groove.
 2. The optical recording medium as claimed in claim 1 wherein the wobbling frequency fw and the pit frequency fp satisfy the relation M fw=N fp where M and N are integers.
 3. The optical recording medium as claimed in claim 1 wherein the pits are formed at substantially constant wobbling positions.
 4. The optical recording medium as claimed in claim 3 wherein the pits are formed at substantially minimum wobbling positions.
 5. The optical recording medium as claimed in claim 3 wherein the pits are formed at substantially maximum wobbling positions proximate to a neighboring turn of the groove.
 6. The optical recording medium as claimed in claim 1 wherein the pits are formed radially in continuation between neighboring turns of the groove.
 7. The optical recording medium as claimed in claim 1 wherein wobbling is of a sole frequency.
 8. The optical recording medium as claimed in claim 1 wherein the sector information is recorded by the pits.
 9. The optical recording medium as claimed in claim 8 wherein said pits have sync pits and/or address pits.
 10. The optical recording medium as claimed in claim 1 wherein the sector information is recorded in the groove by modulating the wobbled signal.
 11. The optical recording medium as claimed in claim 10 wherein the sector information includes the synchronization information and/or the address data.
 12. The optical recording medium as claimed in claim 8 wherein the sector information is recorded in the groove by modulating the wobbled signal.
 13. The optical recording medium as claimed in claim 12 wherein the sector information includes the synchronization information and/or the address data.
 14. The optical recording medium as claimed in claim 12 wherein the sector information of the wobbled signal is at a constant positional relation with respect to the sector information pf the pits.
 15. The optical recording medium as claimed in claim 14 wherein the synchronization signal included in the sector information of the wobbled signal is ahead of the sector information of the pits in the signal reproducing direction.
 16. The optical recording medium as claimed in claim 15 wherein the position of the synchronization signal included in the sector information of the wobbled signal is within one pit period of the sync pits.
 17. A method for recording and/or reproducing signals to an optical recording medium having a wobbled groove and pits formed at a pre-set interval in an area between turns of the wobbled groove, comprising controlling rotation of the optical recording medium by a wobbled signal from the groove and detecting the position on the optical recording medium of a recording signal by pit signals detected from the pits.
 18. The recording and/or reproducing method for the optical recording medium as claimed in claim 17 wherein the wobbled signal and the pit signals are simultaneously read out by a sole beam spot by the push-pull method.
 19. A recording and/or reproducing apparatus comprising: an optical recording medium having a wobbled groove and pits formed at a pre-set interval in an area between turns of the wobbled groove; detection means for detecting a wobbled signal from said groove; and detection means for detecting pit signals from the pits; wherein rotation of the optical recording medium is controlled by the wobbled signals detected from the groove and wherein the position on the optical recording medium of the recording signal is detected by the pit signal detected from the pits.
 20. The recording and/or reproducing apparatus s claimed in claim 19 wherein the detection means for detecting the wobbled signal from said groove and the detection means for detecting pit signals from the pits are detection means for simultaneously reading out the wobbled signal and the pits by a sole beam spot by the push-pull method. 